Relay

A relay is an electronic switch that provides control and isolation between different circuits. It utilizes electromagnetic action to turn output circuits on or off when an input signal is received, eliminating the need for direct physical contact. Relays are used in a wide range of devices and systems, from household appliances to complex industrial automation equipment, all of which rely on relays to perform critical tasks. In this article, we'll take an in-depth look at how relays work, their main types, and their applications.

Principle of operation

A relay consists of five main parts: a coil, a core, contacts, a spring, and a case. When current passes through the coil, it creates a magnetic field that attracts the iron core to push the contacts to move, thus changing the open and closed state of the contacts. This action allows the relay to control between different circuits, for example to make or break the current flow.

Main types

Electromagnetic relays: traditional type of relay that utilizes an electromagnet to operate a switch and is suitable for low frequency switching.

Solid State Relays (SSR): contain no mechanical moving parts and use semiconductor devices to open or close circuits, providing faster response times and longer life.

Thermal Relay: Used for overload protection, it relies on temperature changes to break a circuit and prevent damage to motors or other equipment due to overheating.

Reed Relay: Uses a pair of reed-type contacts that close under the action of a magnetic field. This type of relay is small and responsive and is commonly used in communication equipment.

Specific applications of relays with electronic components

Relays act as control elements in electronic systems, working in concert with other electronic components to realize complex functions. Below are some specific application examples showing how relays can be used in conjunction with other components:

Relays and Sensors

In automated control systems, temperature sensors monitor the ambient temperature and send the data to a microcontroller. Based on this data, the microcontroller controls the relay to activate or deactivate the heating system to maintain the set temperature. This combination application is widely used in domestic heating systems and industrial temperature control equipment.

Relays and Microcontrollers

Relays can be used to extend the output capability of microcontrollers to control high current loads. For example, in smart home systems, microcontrollers control high-power devices such as lamps and motors via relays. This allows the microcontroller to control high-current circuits with simple low-current signals.

Relays and Protection Circuits

In power management systems, relays are often used in conjunction with fuses and current detection circuits to provide overload protection. If current is detected above a safe threshold, the current detection circuit instructs the relay to disconnect the main circuit to prevent further equipment damage.

Relays and Power Supplies

In power supply systems, relays are used to automatically switch the backup power supply. In the event of a mains failure, relays can automatically switch to the standby power supply, ensuring uninterrupted operation of critical equipment such as servers and medical devices.

Contact Resistance Test of Relay

1. Purpose of the test

The main purpose of the contact resistance test is to ensure that the electrical contact between the closed contacts of the relay is good with no unwanted increase in resistance. Good contact quality is essential to maintain efficient current transfer and helps to improve the overall efficiency and reliability of the equipment.

2. Test Procedure

a. Equipment and material preparation:

● High precision microohmmeter or milliohmmeter for measuring very low resistance values.

● Stabilized current source that provides sufficient and constant current to ensure test accuracy.

● Before testing, make sure all connections are clean and in good contact to avoid testing errors.

b. Test Setup:

● Set the relay in the closed state and ensure that the contacts are fully engaged.

● Connect a current source to one side of the contacts and make sure the other side is connected to a voltmeter.

c. Making Measurements:

● Inject a known amount of current (usually a specified or safe value) through the contacts.

● Measure the voltage difference across the contact at both ends of the contact.

● Calculate the contact resistance using the formula R=V/I , where V is the voltage difference and I is the current flowing through the contact.

3. Importance

a. Reduced energy loss: Lower contact resistance helps to minimize the loss of electrical energy to heat, thus improving system efficiency, especially important in high power applications.

b. Prevents overheating and safety hazards: High contact resistance may lead to overheating of the contacts, which in turn affects the structural integrity and functionality of the relay, and may even cause safety incidents such as fires.

c. Ensure relay performance and longevity: Maintaining low contact resistance helps minimize contact material degradation due to high temperatures, extends relay life, and ensures long-term reliability.

d. Compliance with standards and specifications: Adherence to the industry's prescribed standards for contact resistance ensures that relay products are accepted in the global marketplace and avoids the legal and quality risks associated with poor performance.

Performing such tests on a regular basis not only helps maintain the efficiency of the circuit, but is also critical to the long-term operational stability and safety of the device.

Relays play a vital role in modern electronic and electrical systems as a versatile electronic switch. Through synergy with other electronic components such as sensors, microcontrollers and protection circuits, relays not only enable complex control logic, but also play a key role in keeping equipment safe and enhancing system reliability. Their wide range of applications from household appliances to high-end industrial systems highlights their irreplaceable importance.

Rigorous electrical functionality and mechanical durability testing to ensure that each relay maintains its performance and stability in extreme environments is critical to maintaining equipment safety and extending its service life. In this regard, the specialized testing services provided by Rapid Rabbit Laboratories ensure that relays meet the highest quality standards, providing manufacturers and users with additional confidence and security.

As technology advances and market demands change, the design and functionality of relays are evolving to meet more demanding applications. In the future, we can expect relay technology to become even more sophisticated and efficient, continuing to play a central role in the wave of intelligence and automation. With the cutting-edge technology and in-depth industry knowledge of Rapid Rabbit Labs, we have every reason to believe that the evolution of relays will trend towards higher performance and reliability, providing a solid foundation for building a safer and smarter electronic environment.